1. Field of the Invention
The present invention relates to semiconductor wafer testing and, more particularly, to determining the occurrence of soft breakdown of a dielectric layer of a semiconductor wafer.
2. Description of Related Art
Soft breakdown of a dielectric layer occurs when leakage current through the dielectric layer exceeds a predetermined threshold value without causing permanent damage to the dielectric layer. This leakage current can be reversed by reducing the bias applied across the dielectric layer. In contrast, hard breakdown of a dielectric layer is an irreversible, catastrophic breakdown of the dielectric layer that occurs when a high value current flows through the dielectric layer in response to the presence of a very high bias applied across the dielectric layer. Heretofore, soft breakdown of a dielectric layer of a semiconductor wafer was determined by mathematically analyzing acquired current-voltage (IV) data and then determining from the acquired data whether soft breakdown had occurred.
What is needed, however, and is not disclosed in the prior art is an apparatus and method for directly determining the occurrence of soft breakdown of a dielectric layer of a semiconductor wafer that avoids having to mathematically analyze acquired data and make a decision as to whether soft breakdown has actually occurred.